This invention relates to the field of poly(N-vinyl lactam)-urethane gels and more particularly to gels which are skin adhesive and absorbent, which are flexible and contour-conforming, and which can be used in dressings for a variety of applications.
It has been known that polyvinylpyrrolidone (PVP) forms complexes with polyurethanes to yield hydrophilic blends or alloys. U.S. Pat. No. 4,642,267 decribes hydrophilic polymer blends of polyurethane and hydrophilic poly(N-vinyl lactam) prepared in solvent solution to provide slippery coatings when wet and which are water insoluble to some extent once cured by drying. In contrast to the slippery coatings described in U.S. Pat. No. 4,642,267, the dressings of the present invention are tacky gels.
European Patent Application 107,376 describes tacky PVP gels which require the use of ionizing radiation for cross-linking. U.S. Pat. No. 4,646,730 describes a PVP/Silver Sulfadiazine hydrogel dressing in which electron beam radiation is required to cross-link the PVP and form a gel. In addition, magnesium trisilicate, hydrogen peroxide and/or polyacrylic acid are added for color stabilization. It is apparent that there would be an advantage in making tacky skin-adhering gels in the absence of expensive equipment and/or processing.
Ring opening of pyrrolidone groups on PVP was described by H. P. Frank, "The Lactam-Amino Acid Equilibria for Ethylpyrrolidone and Polyvinylpyrrolidone", Journal of Polymer Science 12, 565-576 (1954), and A. Conex and G. Smets, "Ring Opening in Lactam Polymers", J. Poly. Chem. 13, 221-229 (1955). The concept of ring opened pyrrolidone groups is made use of in this invention to unexpectedly attain absorbent and tacky gels.
It is therefore an object of the invention to provide tacky gels having a hydrophilic property.
It is a further object to produce tacky gels without a need for expensive equipment and/or processing.
It is another object to provide tacky gels of poly(N-vinyl lactam) and urethane which can be used in a variety of skin adhesive products.